Explanation:

- The train crosses a bridge of length 80 m in 15 seconds.

- The speed of the train is given as 72 km/h.

- Convert the speed to meters per second: $72\text{ km/h}=72\times \frac{1000}{3600}\text{ m/s}=20\text{ m/s}$.

- Using the formula $\text{Distance}=\text{Speed}\times \text{Time}$, find the total distance covered by the train: $20\text{ m/s}\times 15\text{ s}=300\text{ m}$.

- The total distance includes the length of the train and the bridge.

- Subtract the length of the bridge: $300\text{ m}-80\text{ m}=220\text{ m}$.

- The length of the train is 220 m.